U.S. patent number 9,969,459 [Application Number 13/907,117] was granted by the patent office on 2018-05-15 for right crank arm assembly for a bicycle and crank arm and front sprocket thereof.
This patent grant is currently assigned to Campagnolo S.r.l.. The grantee listed for this patent is CAMPAGNOLO S.R.L.. Invention is credited to Paolo Pasqua, Maurizio Valle.
United States Patent |
9,969,459 |
Valle , et al. |
May 15, 2018 |
Right crank arm assembly for a bicycle and crank arm and front
sprocket thereof
Abstract
A right crank arm assembly for a bicycle, comprises a right
crank arm and at least one front sprocket coupled with the crank
arm at at least one coupling portion of the crank arm. The front
sprocket has an inner side adapted, in use, to face towards the
frame of the bicycle and an outer side opposite the inner side. The
assembly comprises at least one first crank arm element which acts
in contact with the front sprocket on one of said sides and at
least one second crank arm element which acts in contact with the
front sprocket on the other of said sides. The contact action of
the crank arm elements on the two opposite sides of the front
sprocket prevents the twisting deformation of the front sprocket
during pedaling. Such a deformation would cause a reduction in the
transmission efficiency of the right crank arm assembly.
Inventors: |
Valle; Maurizio (Vicenza,
IT), Pasqua; Paolo (Vicenza, IT) |
Applicant: |
Name |
City |
State |
Country |
Type |
CAMPAGNOLO S.R.L. |
Vicenza |
N/A |
IT |
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Assignee: |
Campagnolo S.r.l. (Vicenza,
IT)
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Family
ID: |
37806797 |
Appl.
No.: |
13/907,117 |
Filed: |
May 31, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130291678 A1 |
Nov 7, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11832205 |
Aug 1, 2007 |
8479610 |
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Foreign Application Priority Data
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Aug 3, 2006 [IT] |
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MI2006A1549 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B62M
3/00 (20130101); F16H 55/30 (20130101); B62M
9/105 (20130101); Y10T 74/2164 (20150115); Y10T
74/2165 (20150115) |
Current International
Class: |
B62M
3/00 (20060101); B62M 9/10 (20060101); F16H
55/30 (20060101) |
Field of
Search: |
;74/594.2 |
References Cited
[Referenced By]
U.S. Patent Documents
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Other References
Taiwanese Office Action and Search Report dated Mar. 29, 2013.
cited by applicant .
Japanese Office Action for application No. 2007-202301 dated Aug.
21, 2012. cited by applicant .
Japanese Office Action for Application No. 2007-202302 dated Aug.
21, 2012. cited by applicant .
Japanese Office Action dated Nov. 26, 2013 in corresponding JP
Application No. 2012-245880 and English translation; European
Office Action and Search Report dated Jan. 27, 2014 in
corresponding EP Application No. 12195540.5. cited by
applicant.
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Primary Examiner: Johnson; Vicky A
Attorney, Agent or Firm: Volpe and Koenig, P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a division of U.S. patent application Ser. No.
11/832,205, filed Aug. 1, 2007, which is incorporated by reference
as if fully set forth.
Claims
What is claimed is:
1. A right crank arm assembly for coupling with a bicycle bottom
bracket, the right crank arm assembly comprising: a one piece right
crank arm (5) having a single elongated one piece body (20) that
extends between a first portion (21) configured to couple with a
bicycle pedal and an axle hole (23) including a second portion (22)
configured to couple with a front sprocket, and said right crank
arm (5) includes at least one coupling arm (27) that extends
radially with respect to a defined axis of rotation and terminates
in a first crank arm element (30) that extends circumferentially
with respect to said axis of rotation, and a second crank arm
element (35) that is positioned radially inward from said first
crank arm element (30) and extends from said at least one coupling
arm (27) along a non-radial direction; and at least one front
sprocket (10) has an inner side that, in use, faces towards a frame
of a bicycle and an outer side opposite said inner side that, in
use, faces said right crank arm (5) and couples with said second
portion (22), at least one of said sides of said at least one front
sprocket (10) acts in contact with said first crank arm element
(30) and the other of said sides of said at least one front
sprocket (10) acts in contact with said second crank arm element
(35).
2. The right crank arm assembly of claim 1, wherein said first
crank arm element has an angular extension and acts in contact with
said at least one front sprocket and cooperates with at least one
front sprocket element, wherein, said first crank arm element
angular extension is in the non-radial direction with respect to a
rotational axis of said right crank arm, said at least one front
sprocket element has an angular extension substantially equal to
that of said first crank arm element, said at least one front
sprocket includes an annular element having a radially inner
surface from which at least one coupling element that couples with
said right crank arm extends radially cantilevered, wherein said at
least one coupling element is structurally distinct from said first
crank arm element.
3. The right crank arm assembly of claim 1, wherein said at least
one front sprocket is coupled with said right crank arm at at least
one coupling portion of said at least one front sprocket, wherein
the right crank arm assembly comprises at least one front sprocket
portion which is integral with said at least one front sprocket,
which acts in contact with said right crank arm and which is
structurally distinct from said at least one coupling portion.
4. The right crank arm assembly according to claim 3, wherein said
at least one front sprocket portion is defined in at least one
front sprocket element that extends radially cantilevered from a
radially inner surface of said at least one front sprocket and said
at least one coupling portion is defined in at least one first
coupling element that extends radially cantilevered from said
radially inner surface in a different angular position to that of
said at least one front sprocket element.
5. The right crank arm assembly according to claim 3, wherein said
front sprocket comprises an annular element made from a composite
material.
6. The right crank arm assembly according to claim 3, wherein said
annular element comprises a toothed portion that extends radially
towards the outside along a primitive circumference having a
predetermined diameter T, wherein said at least one front sprocket
element and said at least one first coupling element are entirely
contained in a first area extending radially towards the outside
starting from an ideal circumference having a diameter
T'.gtoreq.aT, where a has a value selected from the group
consisting of: 2/3, 3/4, 4/5, 5/6, and 6/7.
7. The right crank arm assembly according to claim 4, wherein said
first crank arm element is configured to cooperate with said at
least one front sprocket element, and further comprising at least
one second coupling element configured to cooperate with said at
least one first coupling element.
8. The right crank arm assembly according to claim 3, wherein said
right crank arm is made from a composite material.
9. The right crank arm assembly of claim 1, wherein said at least
one coupling arm of said right crank arm comprises a plurality of
coupling arms that are arranged in connected pairs which are
independent of each other.
10. The right crank arm assembly of claim 1, wherein said at least
one front sprocket includes at least one first front sprocket
element that cooperates with said first crank arm element and at
least one second front sprocket element that cooperates with said
second crank arm element, said at least one front sprocket further
comprises an annular element having a radially inner surface from
which at least one coupling element extends radially cantilevered
towards said crank arm, wherein: said annular element comprises a
toothed portion that extends radially towards the outside along a
primitive circumference having a predetermined diameter T, and said
at least one first front sprocket element and said at least one
second front sprocket element are entirely contained in a first
area extending radially towards the outside starting from an ideal
circumference having a diameter T'.gtoreq.aT, where a has a value
selected from the group consisting of: 2/3, 3/4, 4/5, 5/6 and 6/7.
Description
FIELD OF INVENTION
The present invention relates to a right crank arm assembly, crank
arm, and front sprocket for a bicycle.
BACKGROUND
Typically, in the field of bicycles, the expression "right crank
arm assembly" is used to indicate an assembly comprising a right
crank arm and at least one front sprocket coupled with the right
crank arm. The front sprocket, in particular, is the toothed wheel
adapted to drive the chain of the bicycle for the motion
transmission to the rear wheel of the bicycle, such motion being
imparted by the cyclist through pedaling.
In conventional bicycles, the right crank arm is directly coupled
with the front sprocket at respective surfaces defined on
respective front faces of such components. In particular, defining
as inner side of the crank arm and of the front sprocket the one
intended to face, in use, towards the frame of the bicycle and as
outer side the one opposite the inner side and intended to face, in
use, towards the outside, the coupling between right crank arm and
front sprocket typically takes place at one of the sides of the
crank arm and at one of the sides of the front sprocket.
It has been observed that, in operation, the front sprocket
elastically deforms due to the stresses to which it is subjected
during pedaling. Such a deformation leads to a decrease in the
transmission efficiency of the motion imparted through the crank
arm assembly.
In particular, the crank arm transmits to the front sprocket the
force that the cyclist exerts upon the pedals of the bicycle. Such
a force acts in a plane parallel to the middle plane of the front
sprocket and its direction of application and intensity change at
each angular position of the pedal. This stress therefore causes a
variable lateral flexing deformation of the front sprocket.
Considering also that the chain exerts on a portion of the front
sprocket a force opposing the forward movement of the front
sprocket, the resulting stress on the front sprocket is a twisting
stress. Therefore, the consequent deformation of the front sprocket
is a twisting deformation.
Such a deformation occurs in all conventional front sprockets, even
if they are made from metallic material, but it is rather
accentuated in the case of front sprockets made from lightweight
materials.
Indeed, it is known, above all in the field of racing bicycles, to
use front sprockets made from light alloys, like for example
aluminum alloys, and composite alloys, i.e. made partly from
metallic material and partly from another material, like for
example carbon fiber.
The right crank arm assemblies of the prior art typically comprise
a star-shaped right crank arm. Such a crank arms comprise, in
particular, a plurality of coupling arms having at respective free
ends, a portion for fixing to the front sprocket.
The Applicant has found that, in order to reduce the overall weight
of known assemblies to the minimum, the coupling arms of the crank
arms and the corresponding coupling elements of the front sprockets
are made with very low thickness, this causing the twisting of the
front sprockets.
The Applicant has also found that, also in the case of strengthened
crank arms, front sprockets made from light material still continue
to bend a lot.
SUMMARY
The technical problem that the crank arm assembly seeks to overcome
is to reduce as much as possible the twisting deformations of front
sprockets associated with right crank arms, in particular of front
sprockets made from light material, so as not to penalize the
transmission efficiency of the motion imparted through the crank
arm assembly.
The crank arm therefore relates, in a first aspect thereof, to a
right crank arm assembly for a bicycle, comprising a right crank
arm and at least one front sprocket coupled with said crank arm at
at least one first coupling portion of the crank arm, wherein said
at least one front sprocket has an inner side intended, in use, to
face towards the frame of the bicycle and an outer side opposite
the inner side, said assembly further comprising at least one first
crank arm element which acts in contact with said at least one
front sprocket on one of said sides, wherein it comprises at least
one second crank arm element which acts in contact with said at
least one front sprocket on the other of said sides.
BRIEF DESCRIPTION OF THE DRAWINGS
Further characteristics and advantages described herein shall
become clearer from the following detailed description of some
preferred embodiments thereof, made with reference to the attached
drawings. In such drawings:
FIG. 1 is a front view from the inner side of a right crank arm
assembly according to the present invention, comprising a
combination of standard front sprockets;
FIG. 2 is a front view of the outer side of the assembly of FIG.
1;
FIG. 3 is a front view of the inner side of a right crank arm
assembly according to the present invention, comprising a
combination of compact-type front sprockets;
FIG. 4 is a front view of the outer side of the assembly of FIG.
3;
FIG. 5 is a section view according to the section line V-V of FIG.
3;
FIGS. 6 to 8 are respectively a perspective view, a view of the
inner side and a view of the outer side of a right crank arm
according to the present invention, such a crank arm being used in
the assembly of FIG. 1;
FIG. 9 is an enlarged section view according to the line IX-IX of
FIG. 7;
FIGS. 10 and 11 are respectively perspective views of the inner
side and of the outer side of a front sprocket according to the
present invention, such a front sprocket being used in the assembly
of FIG. 1;
FIG. 12 shows a mounting step of the front sprocket of FIGS. 10 and
11 onto the crank arm of FIGS. 6 to 8;
FIG. 13 is a front view of the outer side of an alternative
embodiment of the crank arm described herein;
FIG. 14 is a perspective view of the inner side of an alternative
embodiment of the front sprocket described herein;
FIGS. 15 and 16 are respectively a front view of the outer side and
a perspective view sectioned according to the line XVI-XVI of FIG.
15, of an alternative embodiment of a right crank arm assembly
according to the present invention;
FIG. 17 is a front view of the outer side of a further embodiment
of a right crank arm assembly according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Introduction
Advantageously, the provision in the crank arm of elements adapted
to act in contact with the two opposite sides of the front sprocket
effectively blocks the twisting deformation of the front sprocket
during pedaling, to the great advantage of the transmission
efficiency of the motion imparted through the right crank arm
assembly described herein.
Preferably, the crank arm comprises a main body and said at least
one first crank arm element and at least one second crank arm
element are integral with the main body. However, an alternative
embodiment of the assembly described herein is foreseen in which
said at least one first crank arm element and at least one second
crank arm element are distinct from, and associated with the main
body of the crank arm.
Preferably, the coupling between front sprocket and crank arm at
the aforementioned coupling portion is a dismountable coupling, so
as to be able, if required or necessary, to replace the front
sprocket or the crank arm for maintenance or repairs.
In the preferred embodiments of the assembly described herein, the
crank arm comprises a plurality of first crank arm elements and a
plurality of second crank arm elements. In particular, the crank
arm elements are preferably at least two per side, possibly four,
but embodiments with a different number, even an odd number, of
crank arm elements are not excluded. Advantageously, the provision
of many crank arm elements per side allows a contact between crank
arm and front sprocket to be obtained that is particularly stable
and effective in blocking the twisting deformation of the front
sprocket.
Preferably, at least some of said at least one first crank arm
element and at least one second crank arm element extend at least
partially along respective non-radial directions with respect to a
rotational axis of the crank arm. Advantageously, unlike assemblies
of the prior art where contact occurs only at the ends of the arms
of the crank arm extending radially with respect to the rotational
axis of the crank arm, in the assembly described herein the contact
between front sprocket and crank arm occurs at surfaces having a
greater extension compared to the prior art. The desired stability
and effectiveness of the contact between crank arm and front
sprocket is thus ensured.
Preferably, at least some of said at least one first crank arm
element and at least one second crank arm element extend at least
partially circumferentially around said rotational axis of said
crank arm, more preferably along respective arcs of circumference
having an angular extension of less than 360.degree..
Advantageously, in the crank arm of the assembly described herein,
areas can in this way be identified in which the crank arm elements
are not present. Such areas are used to allow and facilitate the
insertion of the front sprocket between, and its removal from, the
axial space defined on the crank arm between the first and the
second crank arm elements. In this way it is possible to obtain the
contact of the front sprocket with the crank arm at both sides of
the front sprocket at the same time ensuring the removability of
the coupling between front sprocket and crank arm to allow possible
repair or replacement of the front sprocket or crank arm.
Preferably, such an angular extension is less than 360.degree. and
greater than or equal to 15.degree., more preferably it is between
15.degree. and 100.degree., even more preferably between 30.degree.
and 75.degree..
Preferably, said at least one first crank arm element and at least
one second crank arm element act in abutment onto said at least one
front sprocket at different angular positions of the crank arm. The
Applicant has indeed observed that, during pedaling, the front
sprocket twists on different sides from one point to another. The
Applicant has therefore thought to position, at each point of the
front sprocket, crank arm elements only at the side in which the
front sprocket twists. The crank arm elements are thus only
positioned where they actually perform their counteraction to the
twisting deformation of the front sprocket. In this way a
substantial saving in weight of the crank arm is obtained in
addition to an excellent result in terms of prevention of twisting
deformation of the front sprocket.
Preferably, said at least one first crank arm element and at least
one second crank arm element extend from opposite sides with
respect to said at least one first coupling portion. The Applicant
has indeed found that, with reference to a coupling portion with
the crank arm, the front sprocket twists on opposite sides before
and after such a coupling portion, and has thus thought to position
the first crank arm elements on the opposite side to the second
crank arm elements with respect to each coupling portion.
Even more preferably, said at least one second crank arm element is
arranged in a position that precedes said at least one first
coupling portion with reference to the direction of rotation of
said crank arm during pedaling and said at least one first crank
arm element is arranged in a position that follows said at least
one first coupling portion with reference to said direction of
rotation. The Applicant has indeed found that such a geometry
provides effective opposition to the deformation of the front
sprocket.
Preferably, the crank arm comprises at least one abutment surface
adapted to allow the correct angular positioning of the crank arm
with respect to said at least one front sprocket. More preferably,
said at least one abutment surface is defined at least partially in
said at least one second crank arm element. Advantageously, it is
in this way possible to obtain the correct angular positioning of
the crank arm with respect to the front sprocket without needing to
provide special abutment elements. Moreover, the abutment surfaces
advantageously constitute additional means for making the front
sprocket rotate. Indeed, thanks to the provision of the
aforementioned abutment surfaces the right crank arm assembly
described herein would be able to transmit torque in the direction
of pedaling even if the front sprocket is not fixed to the right
crank arm through proper screws.
Even more advantageously, the provision of the abutment surfaces
ensures that when the front sprocket is in abutment onto the crank
arm, the first and second crank arm elements cooperate to hold the
front sprocket in the axial space defined between them, thus
leaving both of the operator's hands free, who can thus easily
screw in the screws to firmly couple the front sprocket with the
crank arm.
In a particularly preferred embodiment thereof, the assembly
described herein comprises a first front sprocket having a first
diameter and at least one second front sprocket having a second
diameter different to the first diameter, wherein the first front
sprocket is coupled with the crank arm at said at least one first
coupling portion and said at least one second front sprocket is
coupled with the crank arm at at least one second coupling portion
different from said at least one first coupling portion.
Advantageously, the provision on the crank arm of different
coupling portions for the different front sprockets makes the
removal of the front sprockets for possible repairs or replacement
quicker and easier. This cannot be obtained in assemblies of the
prior art, wherein all of the front sprockets are coupled with the
crank arms at the same coupling portions of the crank arm.
Even more preferably, said at least one first coupling portion is
defined at a first circumference having its centre at the
rotational axis of the crank arm and said at least one second
coupling portion is defined at at least one second circumference
concentric to the first circumference and having a different
diameter to that of the first circumference.
Advantageously, the provision of front sprockets of different
diameter coupled at different coupling portions of the crank arm
allows a large number of combinations of front sprockets of
different size to be made, such combinations also comprising very
small front sprockets and very big front sprockets. In this
respect, it should be noted that, in conventional assemblies, the
only combinations used are those known as "standard", comprising
small front sprockets with a number of teeth of between 38 and 44
and large front sprockets with a number of teeth of between 52 and
56, and "compact", comprising small front sprockets with a number
of teeth of between 32 and 36 and large front sprockets with a
number of teeth of between 46 and 50. The assembly described
herein, on the other hand, allows different combinations to
"standard" or "compact" to be adopted, like for example mixed
combinations.
The Applicant has also found that, in conventional crank arms, the
arms are sized to give the maximum resistance to twisting in
combination with front sprockets of predetermined size. The result
of this is that, in the case in which the cyclist intends to use
front sprockets of different sizes and wants to maintain an
acceptable structural rigidity, he is forced to replace also the
right crank arm. This, as well as constituting a trouble for the
cyclist, implies that the crank arm manufacturer needs to design,
manufacture and commercialize crank arms of different sizes.
Advantageously, with an assembly like the one described herein in
which front sprockets of different diameter are coupled at
different coupling portions of the crank arm, it is no longer
necessary to produce different sized crank arms for each
combination of front sprockets intended to be used, nor does the
cyclist have to change the crank arm each time he changes the
combination of front sprockets in order to be able to maintain the
desired structural rigidity. The present invention is therefore
advantageous both for the cyclist and for the crank arm
manufacturer.
Preferably, said at least one first coupling portion is defined
along at least one first substantially radial direction with
respect to said rotational axis of the crank arm and said at least
one second coupling portion is defined along at least one second
substantially radial direction different from said first
substantially radial direction.
Even more preferably, the assembly described herein comprises at
least two first coupling portions arranged at a first predetermined
angular distance one from the other and at least two second
coupling portions arranged at a second predetermined angular
distance one from the other, the second predetermined angular
distance being shorter than the first predetermined angular
distance.
In the preferred embodiment of the assembly described herein, the
main body of the crank arm comprises a first body portion that
couples with a bicycle pedal and a second body portion that couples
with said at least one front sprocket and with a shaft of a bottom
bracket assembly of a bicycle, wherein said second body portion
comprises at least one arm that couples with said at least one
front sprocket extending substantially radially with respect to a
rotational axis of the crank arm, wherein said at least one first
coupling portion is defined in said at least one coupling arm and
wherein said at least one first crank arm element and at least one
second crank arm element extend from said at least one coupling arm
along non-radial directions on opposite sides with respect to said
at least one first coupling portion.
Preferably, the crank arm comprises a plurality of coupling arms
and said at least one first crank arm element and at least one
second crank arm element extend from at least some of said coupling
arms.
In particular, in a first particularly preferred embodiment of the
assembly described herein, said at least one second crank arm
element extends cantilevered from a respective coupling arm and,
preferably, said at least one first crank arm element extends
circumferentially without structural interruption between two
adjacent coupling arms. More preferably, said at least one second
crank arm element extends cantilevered from the coupling arm of
said two adjacent coupling arms that precedes the other coupling
arm with reference to the direction of rotation of the crank arm
during pedaling.
However, an embodiment is foreseen in which said at least one first
crank arm element extends cantilevered from a respective coupling
arm.
Preferably, in the case in which the assembly described herein
comprises more than one front sprocket, said at least one second
coupling portion is also defined in said at least one coupling arm.
It is not therefore necessary to provide coupling elements in the
crank arm other than those already provided for the coupling with
the first front sprocket, to the great advantage of the weight of
the crank arm.
Preferably, the crank arm further comprises an additional coupling
portion defined in said first body portion, said first front
sprocket and at least one second front sprocket both being coupled
with said crank arm at said additional coupling portion. In this
way a stable coupling of the front sprockets with the crank arm is
achieved without weakening the body of the crank arm by providing
many coupling points therein.
Preferably, the crank arm is made from light metal material or,
more preferably, from composite material. In the latter case, the
crank arm elements are also made from composite material, so as to
obtain a component which is particularly light in weight.
Preferably, the assembly described herein comprises at least one
first front sprocket element that cooperates with said at least one
first crank arm element and at least one second front sprocket
element that cooperates with said at least one second crank arm
element.
More preferably, said at least one first front sprocket element has
an angular extension substantially equal to that of said at least
one first crank arm element. Advantageously, the front sprocket is
thus provided with extended contact elements that give the front
sprocket itself a certain rigidity and that thus allow the front
sprocket to be made lighter in weight.
Preferably, said at least one front sprocket comprises an annular
element having a radially inner surface from which at least one
coupling element with the crank arm extends cantilevered.
In a preferred embodiment of the assembly described herein, said at
least one first front sprocket element and at least one second
front sprocket element are defined in a body portion of said
annular element extending radially cantilevered from said radially
inner surface and comprising said at least one coupling
element.
In an alternative embodiment of the assembly described herein, said
at least one second front sprocket element is defined by a
respective body portion of said annular element extending radially
cantilevered from said radially inner surface, said respective body
portion not comprising said at least one coupling element.
Preferably, said annular element comprises a toothed portion that
extends radially towards the outside along a primitive
circumference having a predetermined diameter T, and said at least
one first front sprocket element and at least one second front
sprocket element are entirely contained in a first area extending
radially towards the outside starting from an ideal circumference
having a diameter T'.gtoreq.aT, where a has a value selected from
2/3, 3/4, 4/5, 5/6 or 6/7. Advantageously, the front sprocket in
this case is reduced to a simple toothed band provided with contact
and coupling elements with the crank arm having a very short radial
extension.
Preferably, the annular element of the front sprocket is made from
light metal material or composite material. In this way a component
which is particularly light in weight is obtained.
In a second aspect thereof, the present invention relates to a
right crank arm for a bicycle, comprising a main body adapted to be
coupled with at least one front sprocket of a crankset for a
bicycle at at least one first coupling portion of the main body,
said at least one front sprocket having an inner side intended, in
use, to face towards the frame of the bicycle and an outer side
opposite the inner side, the main body comprising at least one
first contact element adapted to act on said at least one front
sprocket on one of said sides, the crank arm being wherein the main
body comprises at least one second contact element adapted to act
on said at least one front sprocket on the other of said sides.
Throughout the present description and in the subsequent claims,
the contact elements described with reference to the crank arm
correspond to the elements indicated previously as crank arm
elements.
Advantageously, the right crank arm described above can be used in
the right crank arm assembly discussed above with reference to the
first aspect described herein, thus allowing the advantages
mentioned above with reference to such a crank arm assembly to be
achieved.
Preferably, the right crank arm described above comprises
individually and/or in combination all of the structural and
functional features (be they essential, preferred and/or
advantageous features) described above with reference to the crank
arm of the right crank arm assembly described herein.
In particular, preferably, said at least one first contact element
and at least one second contact element are integral with the main
body. However, an embodiment is foreseen in which said at least one
first contact element and at least one second contact element are
distinct from, and associated with, said main body.
Preferably, the main body of the crank arm comprises a plurality of
first contact elements and a plurality of second contact
elements.
Preferably, at least some of said at least one first contact
element and at least one second contact element extend at least
partially along respective non-radial directions with respect to a
rotational axis of said crank arm.
Preferably, at least some of said at least one first contact
element and at least one second contact element extend at least
partially circumferentially around said rotational axis of said
crank arm, more preferably along respective arcs of circumference
having an angular extension of less than 360.degree..
Preferably, such an angular extension is less than 360.degree. and
greater than or equal to 15.degree., more preferably it is between
15.degree. and 100.degree., even more preferably between 30.degree.
and 75.degree..
Preferably, said respective arcs of circumference have different
angular positions with respect to said rotational axis.
Preferably, said at least one first contact element and at least
one second contact element extend from opposite sides with respect
to said at least one first coupling portion.
More preferably, said at least one second contact element is
arranged in a position that precedes said at least one first
coupling portion with reference to the direction of rotation of the
crank arm during pedaling and said at least one first contact
element is arranged in a position that follows said at least one
first coupling portion with reference to said direction of
rotation.
Preferably, the main body of the crank arm comprises at least one
abutment surface adapted to allow the correct angular positioning
of said crank arm with respect to said at least one front
sprocket.
More preferably, said at least one abutment surface is defined at
least partially in said at least one second contact element.
Preferably, the main body of the crank arm comprises at least one
first coupling portion with a first front sprocket of a crankset
for a bicycle and at least one second coupling portion with at
least one second front sprocket of a crankset for a bicycle having
a different diameter from the diameter of said at least one first
front sprocket, wherein said at least one second coupling portion
is different from said at least one first coupling portion.
Preferably, said at least one first coupling portion is defined at
a first circumference having its centre at the rotational axis of
said crank arm and said at least one second coupling portion is
defined at at least one second circumference concentric with said
first circumference and having a diameter different to that of said
first circumference.
Preferably, said at least one first coupling portion is defined
along at least one first substantially radial direction with
respect to said rotational axis and said at least one second
coupling portion is defined along at least one second substantially
radial direction different from said first substantially radial
direction.
Preferably, the main body of the crank arm comprises at least two
first coupling portions arranged at a first predetermined angular
distance one from the other and at least two second coupling
portions arranged at a second predetermined angular distance one
from the other, said second predetermined angular distance being
shorter than said first predetermined angular distance.
Preferably, the main body of the crank arm comprises a first body
portion that couples with a bicycle pedal and a second body portion
that couples with said at least one front sprocket and with a shaft
of a bottom bracket assembly of a bicycle, wherein said second body
portion comprises at least one coupling arm with said at least one
front sprocket extending substantially radially with respect to a
rotational axis of said crank arm, wherein said at least one first
coupling portion is defined in said at least one coupling arm and
said at least one first contact element and at least one second
contact element extend from said at least one coupling arm along
non-radial directions on opposite sides with respect to said at
least one coupling portion.
Preferably, said main body comprises a plurality of coupling arms
and said at least one first contact element and at least one second
contact element extend from at least some of said coupling
arms.
In particular, in a first particularly preferred embodiment of the
crank arm described herein, said at least one second contact
element extends cantilevered from a respective coupling arm and,
preferably, said at least one first contact element extends
circumferentially without any structural interruption between two
adjacent coupling arms. More preferably, said at least one second
contact element extends cantilevered from the coupling arm of said
two adjacent coupling arms that precedes the other coupling arm
with reference to the direction of rotation of the crank arm during
pedaling.
However, an embodiment is foreseen in which said at least one first
contact element extends cantilevered from a respective coupling
arm.
Preferably, in the case in which the crank arm described herein is
adapted to be coupled with at least two front sprockets, said at
least one second coupling portion is also defined in said at least
one coupling arm.
Preferably, the main body of the crank arm is made from light metal
material or from composite material.
In a third aspect thereof, the present invention relates to a front
sprocket for a crankset of a bicycle, comprising an annular element
having at least one coupling portion with a right crank arm of a
bicycle, said crank arm having an inner side intended, in use, to
face towards the frame of the bicycle and an outer side opposite
said inner side, said annular element comprising at least one first
contact element adapted to act in abutment on said crank arm on one
of said sides, wherein said annular element comprises at least one
second contact element adapted to act in abutment on said crank arm
on the other of said sides.
Throughout the present description and in the subsequent claims,
the contact elements described with reference to the front sprocket
correspond to the element indicated previously as front sprocket
elements.
Advantageously, the front sprocket described above can be used in
the right crank arm assembly discussed above with reference to the
first aspect described herein and therefore allows the advantages
mentioned above with reference to such a crank arm assembly to be
obtained.
Preferably, the front sprocket described herein comprises
individually and/or in combination all of the structural and
functional features (be they essential, preferred and/or
advantageous features) described with reference to the front
sprocket of the right crank arm assembly of the first aspect
described herein.
In particular, said annular element preferably comprises a
plurality of first contact elements and a plurality of second
contact elements.
Preferably, said at least one first contact element and at least
one second contact element extend at least partially along
respective non-radial directions with respect to a rotational axis
of said front sprocket.
More preferably, said at least one first contact element and at
least one second contact element extend at least partially
circumferentially around said rotational axis of said front
sprocket along respective arcs of circumference having an angular
extension of less than 360.degree..
Preferably, said angular extension is less than 360.degree. and
greater than or equal to 15.degree., more preferably it is between
15.degree. and 100.degree., even more preferably between 30.degree.
and 75.degree..
Even more preferably, said respective arcs of circumference have
different angular positions with respect to said rotational
axis.
Preferably, said at least one first contact element and at least
one second contact element extend from opposite sides with respect
to said at least one coupling portion.
More preferably, said at least one second contact element is
arranged in a position that precedes said at least one coupling
portion with reference to the direction of rotation of the front
sprocket during pedaling and said at least one first contact
element is arranged in a position that follows said at least one
coupling portion with reference to said direction of rotation.
Preferably, said annular element comprises at least one abutment
surface adapted to allow the correct angular positioning of said
front sprocket with respect to said crank arm.
More preferably, said at least one abutment surface is defined at
least partially in said at least one second contact element.
Preferably, said annular element comprises a radially inner surface
from which at least one element for coupling with said crank arm
extends radially, said at least one coupling portion being defined
in said at least one coupling element.
In a first embodiment of the front sprocket described herein, said
at least one first contact element and at least one second contact
element are defined in a body portion of said annular element
extending radially cantilevered from said radially inner surface
and comprising said at least one coupling element.
In an alternative embodiment of the front sprocket described
herein, said at least one second contact element is defined by a
respective body portion of said annular element extending radially
cantilevered from said radially inner surface, said respective body
portion not comprising said at least one coupling element.
Preferably, said at least one first contact element extends
circumferentially without structural interruption between two
adjacent coupling elements.
Preferably, said annular element comprises a toothed portion that
extends radially towards the outside along a primitive
circumference having a predetermined diameter T, wherein said at
least one first contact element and at least one second contact
element are entirely contained in a first area extending radially
towards the outside starting from an ideal circumference having a
diameter T'.gtoreq.aT, where a has a value selected from 2/3, 3/4,
4/5, 5/6 or 6/7.
Preferably, said annular element is made from a light metal alloy
or composite alloy.
In a fourth aspect thereof, the present invention relates to a
right crank arm assembly for a bicycle, comprising a right crank
arm and at least one front sprocket coupled with said crank arm,
wherein it comprises at least one crank arm element which acts in
contact with said at least one front sprocket and that extends
along a non-radial direction with respect to a rotational axis of
said crank arm.
Advantageously, the provision in the crank arm of contact elements
extending along a non-radial direction allows a contact of the
crank arm on the front sprocket to be obtained that is more stable
and effective than what occurs in the assemblies of the prior art,
where the contact occurs only at the ends of the arms of the crank
arm extending radially with respect to the rotational axis of the
crank arm. In this way it is possible to limit the deformation of
the front sprocket, with a consequent advantage in terms of motion
transmission.
Preferably, the assembly discussed above with reference to the
fourth aspect described herein comprises individually and/or in
combination all of the features described above with reference to
the assembly of the first aspect described herein, thus achieving
all of the advantages discussed above with reference to such an
assembly.
In particular, preferably, the crank arm of the assembly of the
fourth aspect described herein comprises at least one coupling arm
with said at least one front sprocket extending along a
substantially radial direction, wherein said at least one crank arm
element extends from said at least one coupling arm.
More preferably, the crank arm comprises a plurality of coupling
arms, wherein said at least one crank arm element extends from at
least some of said coupling arms.
Preferably, said at least one crank arm element extends at least
partially circumferentially around said rotational axis of said
crank arm along an arc of circumference having a predetermined
angular extension.
In a specific embodiment of the assembly described herein, such an
angular extension is equal to 360.degree..
In an alternative embodiment, such an angular extension is less
than 360.degree. and greater than or equal to 15, and is preferably
between 15.degree. and 100.degree., more preferably between
30.degree. and 75.degree..
As already stated with reference to the crank arm assembly
discussed above with reference to the first aspect described
herein, said at least one crank arm element extends
circumferentially without structural interruption between two
adjacent coupling arms. However, a variant is foreseen in which
said at least one crank arm element extends cantilevered from said
at least one coupling arm.
Preferably, said at least one front sprocket has an inner side
intended, in use, to face towards the frame of the bicycle and an
outer side opposite said inner side and said at least one crank arm
element is active on said at least one front sprocket on said outer
side.
Preferably, said crank arm is made from light metal material or
from composite material.
Preferably, the assembly described herein comprises at least one
front sprocket element that cooperates with said at least one crank
arm element, wherein said at least one front sprocket element has
an angular extension substantially equal to that of said at least
one crank arm element.
Preferably, said at least one front sprocket comprises an annular
element having a radially inner surface from which at least one
coupling element with said crank arm extends radially
cantilevered.
Preferably, said at least one coupling element is structurally
distinct from said at least one front sprocket element.
Preferably, said annular element comprises a toothed portion that
extends radially towards the outside along a primitive
circumference having a predetermined diameter T, wherein said at
least one front sprocket element and said at least one coupling
element are entirely contained in a first area extending radially
towards the outside starting from an ideal circumference having a
diameter T'.gtoreq.aT, where a has a value selected from 2/3, 3/4,
4/5, 5/6 or 6/7.
Preferably, said annular element is made from light metal material
or from composite material.
In a fifth aspect thereof, the present invention relates to a right
crank arm for a bicycle, comprising a main body adapted to be
coupled with at least one front sprocket of a crankset of a
bicycle, wherein said main body comprises at least one contact
element with said at least one front sprocket that extends along a
non-radial direction with respect to a rotational axis of said
crank arm.
Throughout the present description and in the subsequent claims,
the contact elements described with reference to the crank arm
correspond to the elements indicated previously as crank arm
elements.
Advantageously, the crank arm described above can be used in the
right crank arm assembly discussed above with reference to the
fourth aspect described herein, and thus allows the advantages
mentioned above with reference to such a crank arm assembly to be
achieved.
Preferably, the crank arm described herein comprises individually
and/or in combination all of the structural and functional features
(be they essential, preferred and/or advantageous features)
described with reference to the crank arm of the right crank arm
assembly of the fourth aspect described herein.
In a sixth aspect thereof, the present invention relates to a front
sprocket for a crankset of a bicycle, comprising an annular element
adapted to be coupled with a right crank arm of a bicycle, wherein
said annular element comprises at least one contact element with
said crank arm extending along a non-radial direction with respect
to a rotational axis of said front sprocket.
Throughout the present description and in the subsequent claims,
the contact elements described with reference to the front sprocket
correspond to the elements indicated previously as front sprocket
elements.
Advantageously, the front sprocket described above can be used in
the right crank arm assembly discussed above with reference to the
fourth aspect described herein, and therefore allows the advantages
mentioned above with reference to such a crank arm assembly to be
achieved.
Preferably, the front sprocket described herein comprises
individually and/or in combination all of the structural and
functional features (be they essential, preferred and/or
advantageous features) described with reference to the front
sprocket of the right crank arm assembly of the fourth aspect
described herein.
In a seventh aspect thereof, the present invention relates to a
right crank arm assembly for a bicycle, comprising a right crank
arm and at least one front sprocket coupled with said crank arm at
at least one coupling portion of said at least one front sprocket,
wherein it comprises at least one front sprocket portion which acts
in contact with said crank arm and which is structurally distinct
from said at least one coupling portion.
Advantageously, the provision in the front sprocket of contact
portions which are structurally distinct from the coupling portions
allows a contact of the crank arm to be made on the front sprocket
that is more stable and effective that what occurs in the
assemblies of the prior art, where the contact only occurs at the
ends of the arms of the crank arm extending radially with respect
to the rotational axis of the crank arm. In this way it is possible
to limit the deformation of the front sprocket, with a consequent
advantage in terms of transmission of motion.
Preferably, the assembly discussed above with reference to the
seventh aspect described herein comprises individually and/or in
combination all of the structural and functional features discussed
above with reference to the assembly of the first aspect described
herein, thus obtaining all of the advantages discussed above with
reference to this assembly.
In particular, preferably, said at least one front sprocket portion
is defined in at least one front sprocket element that extends
radially cantilevered from a radially inner surface of said at
least one front sprocket and said at least one coupling portion is
defined in at least one first coupling element that extends
radially cantilevered from said radially inner surface in a
different angular position to that of said at least one front
sprocket element.
Preferably, said front sprocket comprises an annular element made
from a light metal material or from a composite material.
Preferably, said annular element comprises a toothed portion that
extends radially towards the outside along a primitive
circumference having a predetermined diameter T, wherein said at
least one front sprocket element and said at least one first
coupling element are entirely contained in a first area extending
radially towards the outside starting from an ideal circumference
having a diameter T'.gtoreq.aT, where a has a value selected from
2/3, 3/4, 4/5, 5/6 or 6/7.
Preferably, the assembly described herein comprises at least one
crank arm element adapted to cooperate with said at least one front
sprocket element and at least one second coupling element adapted
to cooperate with said at least one first coupling element.
Preferably, said crank arm is made from a light metal material or
from a composite material.
In an eighth aspect thereof, the present invention relates to a
front sprocket for a crankset of a bicycle, comprising an annular
element adapted to be coupled with a right crank arm of a bicycle
at a coupling portion of said annular element, wherein said annular
element comprises at least one contact portion with said crank arm
which is structurally distinct from said at least one coupling
portion.
Throughout the present description and in the subsequent claims,
the contact elements described with reference to the front sprocket
correspond to the elements indicated previously as front sprocket
elements.
Advantageously, the front sprocket described above can be used in
the right crank arm assembly discussed above with reference to the
seventh aspect described herein, and thus allows the advantages
mentioned above with reference to such a crank arm assembly to be
obtained.
Preferably, the front sprocket described herein comprises
individually and/or in combination all of the structural and
functional features (be they essential, preferred and/or
advantageous features) described with reference to the front
sprocket of the right crank arm assembly of the seventh aspect
described herein.
DESCRIPTION
With reference to FIGS. 1 and 2, a first embodiment of a right
crank arm assembly according to the present invention is indicated
with 1. The assembly 1 comprises a right crank arm 5, a front
sprocket of larger diameter 10 (hereafter indicated as big front
sprocket) and a front sprocket of smaller diameter 15 (hereafter
indicated as small front sprocket). Alternative and not illustrated
embodiments are foreseen in which the assembly 1 comprises just one
front sprocket, for example for use on a racing track, or more than
two front sprockets, for example three.
Throughout the present description and in the subsequent claims,
the "inner side" of the assembly 1, of the crank arm 5 and/or of
the front sprockets 10 and 15 shall indicate the side visible in
FIGS. 1 and 3, i.e. the one facing towards the frame of the bicycle
when the assembly 1 is mounted in the bottom bracket assembly. On
the other hand "outer side" shall indicate the side opposite the
inner side, visible in FIGS. 2 and 4.
Throughout the present description and in the subsequent claims,
moreover, "previous position" or "following position" shall
respectively indicate the position of an element that precedes and
that follows a reference element in the direction of rotation of
the crank arm, where the rotation is in the direction such as to
transmit driving force to the rear wheel.
The right crank arm 5 described herein can be made from metallic
material, like a light alloy, or from composite material,
comprising structural fibers incorporated in a polymeric material.
Typically, the structural fibers are selected from the group
consisting of carbon fibers, glass fibers, aramid fibers, ceramic
fibers, boron fibers and combinations thereof, carbon fibers being
preferred. Preferably, the polymeric material of the body of the
component is thermosetting. However, the possibility of using a
thermoplastic material is not excluded. More preferably, the
polymeric material comprises an epoxy resin. While these materials
are preferred, they are not limiting to other materials that may be
chosen.
The arrangement of said structural fibers in the polymeric material
can be a random arrangement of pieces or sheets of structural
fibers, a substantially unidirectional ordered arrangement of
fibers, a substantially bidirectional ordered arrangement of
fibers, or a combination of the above.
In an alternative embodiment, the fibers are organized in a fabric
wound with continuity around a recess, as described in patent EP
1270394 and in European patent applications no 06425086 and
06425087 (U.S. application Ser. Nos. 11/675,279 and 11/501,656) to
the same Applicant the content of which are incorporated herein by
reference as if fully set forth.
With particular reference to FIGS. 6 to 8, the right crank arm 5
comprises a main body 20 having a first end 21 for coupling with a
pedal (not illustrated) and a second end 22 for coupling with the
front sprockets 10 and 15 and with a shaft of a bottom bracket
assembly (not illustrated). In particular, the second end 22
comprises a hole 23 for housing the shaft of the bottom bracket
assembly. In alternative and not illustrated embodiments but known
to a person of ordinary skill in the art, the shaft is removably
coupled with the right crank arm, or it is an integral part
thereof.
A support structure 25 of the front sprockets 10 and 15 is provided
about the hole 23, comprising four coupling arms (or spokes) 27
that extend substantially radially around the hole 23 inside of
which a rotational axis X of the crank arm 5 is defined.
At the respective free end portions 28 the arms 27 are connected in
sets of two by a reinforcing element 30, preferably extending
circumferentially around the rotational axis X of the crank arm 5
and made in the form of an arc of circle.
Each reinforcing element 30 that connects a pair of arms 27
comprises a contact surface 32 at the outer side of the big front
sprocket 10.
The contact surfaces 32 preferably have an angular extension
.alpha. (FIG. 7) greater than or equal to 15.degree., preferably
between 15.degree. and 100.degree., more preferably between
30.degree. and 75.degree. and are arranged at an angular distance
.beta. from the middle plane .PI. of the elongated body 20, where
.beta. is preferably between 30.degree. and 90.degree..
In an alternative embodiment of the crank arm 5 (not illustrated)
the pairs of arms 27 connected by the element 30 are replaced by a
single arm of equal angular extension.
Now considering the pairs of arms 27 connected together by the
element 30, the arm 27 of each of them coming first in the
direction of rotation .omega. of the right crank arm 5 around the
rotational axis X of the crank arm 5, comprises an element 35
extending cantilevered in the circumferential direction in the
direction of rotation .omega.. Each element 35 comprises a contact
surface 40 at the inner side of the big front sprocket 10.
Coupling portions 44 with the big front sprocket 10 are defined at
the free ends 28 of each arm 27. The element 30 connects the
coupling arms 27 right at such coupling portions 44. The coupling
portions 44 are provided with coupling holes 45.
The coupling portions 44 with the ends 28 of the arms 27 connected
by the element 30 are arranged at an angular distance .gamma. from
each other of between 45.degree. and 95.degree., and the coupling
portion 44 closest to the elongated body 20 is arranged at an
angular distance .mu. of between 35.degree. and 85.degree. from the
plane .PI..
An additional coupling hole 46 with the front sprocket 10 is
preferably provided on a portion of the elongated body 20 (FIG.
7).
The section of FIG. 9 shows in detail an example embodiment of the
coupling portions 44 in the case in which the right crank arm 5 is
made from composite material. The coupling portions 44 are in this
case preferably defined by metallic inserts 50 provided with a
threaded hole 52 for the insertion of a screw (not illustrated).
The outer surface 54 of the inserts 50 is irregular, and preferably
threaded, so as to be able to be better held in the composite
material, to which it is fixed by gluing or by direct adhesion due
to a co-moulding process.
An alternative embodiment of the assembly described herein is
foreseen in which the threaded hole 52 is directly made in the
composite material.
As shown in detail in FIG. 9, the crank arm 5 described herein
further comprises, in a preferred embodiment thereof, second
coupling portions 47 used for the coupling of the small front
sprocket 15. The coupling portions 47 are preferably made identical
to the coupling portions 44 and comprise coupling holes 48.
The coupling portions 44 and 47 are at different distances from the
rotational axis X of the right crank arm 5. In particular, their
axes of symmetry S1 and S2 lie on two ideal circumferences of
different diameter.
As illustrated in FIGS. 1, 3, 6, 7 and 12, the coupling portions 44
and 47 are preferably non-radially aligned with each other. Indeed,
the coupling portions 44 are at smaller angular distances .gamma.
apart than the angular distances between the coupling portions
47.
Both the big front sprocket 10 and the small front sprocket 15 are
coupled with the main body 20 of the crank arm 5 at the additional
coupling portion 46.
With particular reference now to the section illustrated in FIG. 5,
in a preferred embodiment described herein the contact elements 30
and 35 respectively at the outer side and at the inner side of the
big front sprocket 10 are located substantially at the opposite
side with respect to the coupling portions 44, identified by the
axis of symmetry S1 (said axis is parallel to the rotational axis x
of the crank arm 5). In particular, the surface 32 of the element
30 for contact at the outer side of the front sprocket 10 follows
the coupling portion 44 in the direction of rotation .omega.,
whereas the surface 40 of the element 35 for contact at the inner
side of the front sprocket 10 precedes the coupling portion 44
(FIGS. 6 and 7). The elements 30 and 35 are therefore active in
abutment on the front sprocket at different angular positions. It
should be appreciated from FIG. 5 that the first contact element 30
and the second contact 40 element are offset from one another along
the rotational axis of the right crank arm 5; this offset creates a
gap in which the front sprocket 10 is engaged.
In an alternative embodiment of the crank arm illustrated in FIG.
13 and indicated with 5', the arms 27' instead of being connected
in sets of two through the elements 30, each comprise an element
30' extending cantilevered circumferentially around the rotational
axis X of the crank arm 5'. Each element 30' comprises a respective
contact surface 32' at the outer side of the big front sprocket 10.
Each of the arms 27' also comprises a respective contact surface
40' at the inner side of the big front sprocket 10. The contact
surfaces 32' and 40' are arranged in a position respectively prior
to and after the coupling portion 44 (hidden in the figures)
provided on the arm 27. In this case, the number of arms 27 can
also be odd, for example three or five.
In a further not illustrated embodiment of the assembly described
herein, just one or in any case just a few of the arms 27 comprise
a contact surface 40 at the inner side of the big front sprocket
10, between which the arm 27 immediately following the elongated
body 20 with reference to the direction of rotation .omega. of the
crank arm 5 and preferably the arm 27 arranged in a substantially
symmetrical position with respect to the main body 20 of the crank
arm 5.
In accordance with the invention, the contact surfaces 32 and 40 do
not lie on the same plane, but a predetermined axial distance D
apart (FIG. 5). In this way the big front sprocket 10 does not need
to be deformed to be inserted between the two contact surfaces. It
is thus sufficient for the front sprocket 10 to have a thickness
equal to D in the contact area with the crank arm 5. Preferably D
is equal to or less than the maximum thickness of the big front
sprocket 10.
In the embodiments illustrated in the attached figures, the
elements 30 and 35 are integral with the main body 20 of the crank
arm 5, but in other not illustrated embodiments such elements can
be made in separate pieces and coupled with the crank arm 5.
In FIGS. 10 and 11, the big front sprocket 10 of the right crank
arm assembly 1 shown in FIGS. 1 and 2 is illustrated.
Such a front sprocket comprises an annular element 11, preferably
made from light metal alloy or from composite material, having a
radially outer annular surface 12 on which a toothed portion 100
(hereafter also indicated as toothing) is formed extending radially
towards the outside and a radially inner annular surface 13 from
which four elements 98 for coupling with the crank arm extend
radially cantilevered. In particular, the elements 98 are adapted
to be coupled with the arms 27 of the crank arm 5 by coupling
respective coupling portions defined on the elements 98 with the
coupling portions 44 defined on the arms 27. The coupling takes
place through screws (not illustrated) inserted in holes 64 formed
on each coupling element 98.
On outer side thereof (FIG. 11) the big front sprocket 10 comprises
two elements 55 having respective contact surfaces 60 adapted to
contact the contact surfaces 32 of the elements 30 of the right
crank arm 5. The elements 55 have the same angular extension as the
elements 30 and each element 55 extends without structural
interruption between two adjacent elements 98. What has been stated
above with reference to the number, angular position with respect
to the coupling portions 44 and angular extension of the elements
30 of the crank arm 5 with respect to the rotational axis of the
crank arm is therefore also valid for the elements 55 of the front
sprocket 10 with reference to the coupling portions defined on the
elements 98 and with reference to the rotational axis of the front
sprocket.
The elements 55 are preferably surmounted in the radial direction
by a throat 62 extending according to an arc of circle.
At the ends of the elements 55 the holes 64 for the passage of the
screws that insert into the inserts 50 of the right crank arm 5 are
formed.
On the inner side of the front sprocket 10 (illustrated in FIG.
10), on the other hand, a pair of elements 65 are provided having
respective contact surfaces 66 adapted to contact the contact
surfaces 40 of the elements 35 of the right crank arm 5.
The big front sprocket 10 further comprises an additional arm 68
with a hole 69 for the passage of a screw intended to insert into
the hole formed in the additional coupling portion 46 of the crank
arm 5, in the case in which such an additional coupling portion is
present.
In the embodiment of the big front sprocket 10 illustrated in
detail in FIGS. 10 and 11, each contact element 55 and 65 with the
crank arm 5 is defined at a single body portion 14 of the annular
element 11 that extends radially cantilevered towards the centre of
the front sprocket 10 from inner surface 13 thereof and that also
comprises a pair of coupling elements 98. The elements 55, 65, and
98 are therefore all an integral part of the body portion 14.
FIG. 14 shows an alternative embodiment of the big front sprocket,
indicated with 10. In such an embodiment no single body portion 14
that comprises the elements 65 and 98 can be identified. Indeed,
the body portion 14 here comprises just the contact element 55 and
a pair of elements 98 for coupling with the crank arm 5, whereas
the contact elements 65 with the crank arm are defined at further
and respective body portions 140, distinct and separate from the
body portion 14 of the annular element 11, which also extend
radially cantilevered from the inner surface 14 of the annular
element 11 towards the centre of the front sprocket 10 and which do
not comprise the coupling elements 98 and the contact elements 55
with the crank arm 5.
In such an embodiment, the elements 98 and 65 are made adjacent to
the toothed portion 100 of the front sprocket 10. Preferably,
considering the diameter T of the primitive circumference of the
toothed portion 100, the elements 98 and 65 are located and
entirely contained in an annular area extending radially between
the inner surface of said annular element and an ideal
circumference of diameter T' such that T>T'.gtoreq.aT, where a
is selected from 2/3, 3/4, 4/5, 5/6 or 6/7.
Preferably, the aforementioned inner surface is defined at an ideal
circumference arranged at least 1 mm radially towards the inside
from the toothed portion 100.
The front sprocket 10 in this case therefore reduces to a toothed
band provided with radial projections constituting the coupling
elements 98 and the contact elements 55 and 65 and having a short
radial extension. Consequently, the maximum radial extension of the
coupling arms provided in the crank arm is defined by a
circumference of diameter T'' (see FIGS. 2 and 4) such that
T>T''>T', where the difference between T and T'' is simply
given by the need to leave a free front sprocket portion which is
sufficient to allow the engagement of the teeth with a chain.
With particular reference to FIG. 4, if L indicates the length of
the arm of the crank arm (such a length being commercially set at
170 mm, 172.5 mm and 175 mm), the crank arm of the assembly
described herein is sized so that the ratio L/T'' is between 0.7
and 1, preferably between 0.8 and 0.9.
A not illustrated embodiment is foreseen in which the front
sprocket has coupling elements 98 and contact elements 55 and 65 of
short extension as described above with reference to FIG. 14 and
all forming part of a single body portion 14 as described above
with reference to FIG. 11.
It should be noted how, in all of the embodiments of the front
sprocket 10 of the assembly described herein, the contact portions
of the front sprocket 10 with the crank arm 5 are structurally and
physically distinct from the respective coupling portions.
In the case of use of the front sprocket of FIG. 11 or of the not
illustrated embodiment in which the front sprocket has coupling
elements 98 and contact elements 55 and 65 of short extension as
described above with reference to FIG. 14 and all forming part of a
single body portion 14 as described above with reference to FIG.
11, the crank arm of the assembly described herein has coupling
arms having a greater radial extension than those of conventional
crank arms. In particular, while in conventional crank arms the
diameter of the ideal circumference defined by the coupling holes
at the big front sprocket and at the small front sprocket is 130 mm
or 135 mm in the case of standard combinations and 110 mm in the
case of compact combinations, in the crank arm of the assembly
described herein the diameter of the ideal circumference defined by
the holes 45 for coupling with the big front sprocket 10 is within
an annular area having an inner diameter greater than or equal to
150 mm and an outer diameter less than or equal to 180 mm,
preferably an inner diameter greater than or equal to 160 mm and an
outer diameter less than or equal to 170 mm, whereas that of the
ideal circumference defined by the holes 48 for coupling with the
small front sprocket 15 is within an annular area having an inner
diameter greater than or equal to 100 mm and an outer diameter less
than or equal to 130 mm, preferably an inner diameter greater than
or equal to 110 mm and an outer diameter less than or equal to 120
mm.
FIGS. 1 and 2 show a right crank arm assembly comprising a
combination of standard front sprockets, i.e. a small front
sprocket with a minimum of 39 teeth coupled with a big front
sprocket with a number of teeth of between 52 and 56 (53 in the
front sprocket 10 illustrated).
However, the right crank arm 5 illustrated in FIGS. 6, 7 and 8 can
support a wide range of combinations of front sprockets, for
example a compact combination, as illustrated in FIGS. 3 and 4, in
which the small front sprocket 15' has a minimum number of teeth
equal to 34 and the big front sprocket 10' has a number of teeth of
between 46 and 50 (48 in the combination illustrated).
It should however be noted that the right crank arm 5 allows any
size of front sprockets to be mounted, for which reason it is also
possible to adopt combinations of front sprockets different to the
standard and compact ones, in particular mixed combinations.
As illustrated in FIGS. 6, 7, 8, 13, the crank arm 5, 5' further
comprises abutment surfaces 70, 70' adapted to allow the correct
angular positioning of the crank arm with respect to the front
sprocket 10. Such surfaces 70, 70' are defined at a free end of the
contact element 35, 35' with the crank arm 5, 5'. Further abutment
surfaces 72 are provided at a body portion of the element 35 that
extends on the opposite side, with respect to the coupling arm 27,
to the one at which the abutment surface 70 is defined. The
abutment surfaces 70 and 72 cooperate in abutment with
corresponding abutment surfaces 74, 76 defined in the big front
sprocket 10.
FIG. 12 illustrates the way to mount a big front sprocket 10 on a
right crank arm 5. In particular, the big front sprocket 10 is
brought in contact with the right crank arm 5 so that the contact
surfaces 32 of the elements 30 of the crank arm 5 come into contact
with the contact surfaces 60 of the elements 55 of the front
sprocket 10. At this point the right crank arm 5 is rotated with
respect to the front sprocket 10 in the same direction of rotation
.omega. in which it rotates during pedaling. The crank arm 5 shall
move with respect to the front sprocket until the abutment surfaces
70 and 72 of the right crank arm 5 make contact with the
corresponding abutment surfaces 74 and 76 of the front sprocket 10.
At this point, the contact surfaces 40 of the elements 35 of the
crank arm 5 shall be in abutment with the contact surfaces 66 of
the elements 65 of the front sprocket 10. As a result of this, when
the surfaces 74 and 76 of the front sprocket 10 are in abutment
with the surfaces 70 and 72 of the crank arm, the contact surfaces
32, 40, 60 and 66 cooperate with each other to keep it in position
and the operator has both hands free to fix the screws.
It should be appreciated that the first contact element 55 and the
second contact element 65 are offset from one another along a
rotational axis of the annular element 11.
Now with reference to FIGS. 15 and 16, a further embodiment of the
right crank arm assembly according to the present invention is
illustrated, indicated with 200.
The right crank arm assembly 200 comprises a right crank arm 205,
preferably made from composite material, comprising a coupling
portion 210 with an annular toothed band 215. The coupling portion
210 preferably comprises an annular-shaped outer peripheral portion
225 coupled with the elongated body 220 of the crank arm 205
through a plurality of coupling arms 230.
The coupling between the coupling portion 210 and the toothed band
215 can be of any type capable of transmitting torque. In FIG. 16,
as an example, a shape-coupling is illustrated, in particular
toothed, preferably strengthened by gluing, or by the adhesion
between composite material of the coupling portion 210 and the
metal of the toothed band 215 obtained by co-molding.
Alternatively, the toothed band 215 and the coupling portion 210
could be made with a threading at their interface to be screwed
(and then possibly glued) one to the other. According to a further
alternative, the toothed band 215 is fixed onto the coupling
portion 210 through screws or other fastening elements.
It should be observed that, although FIG. 16 shows a radial
coupling interface 240 and a circumferential coupling interface
245, it does not exclude embodiments in which the coupling is just
circumferential or just radial (in which case there are no front or
rear contact surfaces as for the embodiments of FIGS. 1 to 14). The
coupling between the toothed band 205 and the coupling portion 210
could also be a dovetail coupling, or a coupling extending along a
surface inclined with respect to the rotational axis of the annular
toothed band 215.
It should also be observed that, although in FIG. 15 just one
annular toothed band 215 is shown, an embodiment is foreseen in
which the right crank arm 205 is also coupled with a front sprocket
or annular band of smaller diameter. The coupling between such an
annular band of smaller diameter and the right crank arm 205 is of
the same type as that described with reference to the annular
toothed band 215.
As highlighted in the variant 200' of FIG. 17, the coupling portion
210', instead of being extended according to a complete ring, can
comprise ring portions 225', for example having the dimensions
illustrated with reference to the support structure 25 of the crank
arm 5 of FIGS. 6, 7 and 8. The coupling between the coupling
portion 210' and the annular toothed band 215' is of the same type
described for the assembly 200 of FIGS. 15 and 16.
FIG. 17 also shows that the right crank arm assembly 200' (just
like the one 200 of FIG. 15) can comprise a second front sprocket
or toothed band 216 of smaller diameter with respect to the toothed
band 215'. The small front sprocket 216 can be of the type
illustrated with reference to the right crank arm assemblies of
FIGS. 1 to 4, or else a toothed band similar to the toothed band
215', coupled with the crank arm 205' in the same way as the
toothed band 215'.
In all of the embodiments described and illustrated, the small
front sprocket 15 is coupled with the right crank arm 5 in a
conventional way, i.e. contacting just the outer side. However, an
embodiment is foreseen in which the coupling between the small
front sprocket 15 and the crank arm 5 is the same as that described
for the big front sprocket 10, i.e. contacting both the outer side
and the inner side.
Numerous variants of the right crank arm 5 are possible, for
example the position of the contact elements at the outer side and
at the inner side of the big front sprocket can be inverted with
respect to the coupling portions, thus performing their contact
function in different angular positions of pedaling. The
illustrated example is that in which the contact elements
counteract the twisting of the front sprocket in the most critical
condition, i.e. when the pedal has passed the vertical to begin a
new descent, since this is the point at which the cyclist exerts
the maximum thrust. The contact surfaces can also face each other
and therefore are at an identical angular position.
* * * * *